Truing apparatus for centerless machines



Jan. 25, 1949. CROMPTONY JR 2,459,923

' TRUING APPARATUS FOR CENTERLESS MACHINES Filed March 8, 1946 .2 Sheets-Sheet l Jafh; 25,1949. GCFwMP ON, R 2,459,923

IRUING APPARATUS FOR CENTERLES MACHINES Filed March 8, 1946 2 Sheets-Sheet 2 Patented Jan. 25, 1949 I TRUiNG APPARATUS FOR GENTERLESS MACHINES G rge G ompten.

, r F amin am, Mass, a gn r to No ton Qomp any, Worcester, Mass,

a corporation of Mas usett Application M rch :8, 1946, Ser al. No 55332.

Qlaimsl The invention relates to t e apparatus or centerless machines, that is for grinding ma-v chine and lapping machines, and with regard to its more specific features for truing the feed wheel or wheels Whether the regulating wheel or gr nd wheel or bo h- .One obi-ct of the invention is 170 provide a truing apparatus which can be adjusted for ,di-f-i ferent sizes of work pieces. Another object of the invention is to provide a trujng apparatus which will true feed wheels to a perfect shape or more nearly perfect shape. Another object of the invention is; to provide truing apparatus which will permit the use of wide wheels such as are desirable, for example, for centerless lapping machin no r obje t s t or t the r ors of truing standard .centerless machines.

Another object is to provide, in a machine oi e c ar cter i di ated, a mp adjustment scaled to the size of the work pieces for changing action of t t ai s po -nt- Anct er obj ct the invention is to provide a mechanism whereby a truing diamond-can be moved a straight line r in a slightly curved line. An-

other object of the invention to provide a iced 1 wheel to gear perfectly with a given size of work piece at a skew angle to the wheel. Another object s to perm t the use of eater an les f skew of a regulating or feed wheel without sacrie ficing accuracy in grinding or lapping other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the den..- u s of construction, om inat ons of ele ents. and arra g en o p rts, as will he exemplified in e structure to. be hereina ter descr bed a d the scope of the application of which w i ll be in..- dicated in the following claims.

In the accompanying drawings in which is shown one of yarious possible embodiments of the mechanical Ieatures of this-invention,

Figure 1 is a plan view of the apparat s,

Y Figure 2 is a cross sectional view eta-ken on {the ne e.f F gure the ab as e t d wh however, being shown in elevation,

- Figure 3 is a front elevation ofa modification of the long bar show n adjustable s pn s therefor whereby the curved surface open which the follower travels may be adjusted to allow for variations of the position of the wQrk p169? 2. l'

t i ding threat, the supporting p ss fleeing shown in section, isu e is a side elevation of the long par and adjustable support pf Fig-mg 3,

As conducive to a better unde fiirnfli-llg @i l ke A 2 present invention some observations about cene terless grinders, the feed wheel thereof, and the truing apparatus therefor will be made. In a centerles's grinder set up for through feed grinding the regulating wheel is adjusted so that its axis is at a angle to the axis of the work piece when the work piece is on the work rest. This angle, called the skew angle, imparts a feeding component to the work piece to move it through the grinding throat. It is common practice to set this angle at about five degrees more or less, and extreme angles have been avoided. It is also common practice when setting up the machine for infeed grinding to place the regulating wheel at a small skew angle, for example one degree, to give a slight feeding component to hold the work piece against a stop.

' A cylinder will mesh perfectly with another cylinder provided their axes are parallel, and a cone will mesh with another cone or with a cylinder provided their axes are in a plane. But if two cylinders have non-parallel axes they can be made to touch only at a point and similarly for cones or cylinders if their axes are not in a single plane.

1 f, however, a t-ruing diamond is moved to cut a regulating wheel by moving the diamond in a line skewed to the of the regulating wheel by the same amount that the axis of the regulating wheel is skewed to the axis of the work piece, a regulating wheel is produced which appears to mesh with cylindrical work piece. This is the customary practice and for many grinding operations the results are close enough to perfecr tion for all practical purposes.

But I have been aware for a long time that a perfect re ulating or feed wheel is not thereby produced since no allowance or adjustment is "made for difierent sizes of work pieces. Even if an adjustment were made, within the capabilities of the present machine, there still would not he produced a perfectlcgulating wheel.

To show that regulating wheels as at present trued are not perfect, it should suffice to show that different shapes of regulating wheels are required for different sizes of work pieces. Let us consider all possible sizes of work pieces referring to the diameter. Such sizes of diameters extend from zero to infinity. A cylindrical work piece of zero diameter which of course cannot exist, will mesh perfectly with a regulating wheel trued as above described because the diamond th e e c lv has a poin h h e th c tting. practically this is nearly true because dia onds av sh p po y ed a ng o course the diamond point moves in a straight line and you can lay a straight line along a straight line. It is believed that the regulating wheel thus produced is a hyperboloid which is defined as a hyperbola of revolution revolved about its axis of symmetry.

Considering the other extreme condition, where the diameter of the work piece is infinity, we have a work piece surface which is a plane. Now it is known that a plane will not mesh with a hyperboloid. Therefore it follows that work pieces of finite diameter will mesh with different surfaces depending upon the particular diameter of the particular work piece. In fact, this canbe shown graphically.

To true a regulating or feed wheel properly, I

move the diamond along a curved surface, which 7 I believe should be a hyperbolic surface, to correct the action of the truing tool. This, according to the present invention, may be done by providing a follower 'on the truing tool post and a cam of hyperbolic cylindrical surface, and means for adjusting the cam. For example, if we had a work piece of zero diameter the cam would be set so that the follower would move along an element of the hyperbolic cylinder which is of course a straight line. But for work pieces of finite diameter feet the cam at an angle, the larger the work piece the larger the angle, thus causing thefollower to move along hyperbolae of varying asymptotic angles.

Two conditions should be pointed out. In the first place while present machines produce very good work pieces it' may be desirable to make a lapping machine with very'wide wheels, whereupon the errror in present machines would be material. Also for fast through feeding or for other purposes, it may be desirable greatly to increase the skew angle. Again the error of present machines would become material. On the other hand, since present machines are commercially useful and since moving the diamond in a curve causes the results to approach perfection for some machines and skew angles it will be suflicient to approximate perfection as by use of a cam having a surface otherthan a hyperbolic cylinder, for example, having a surface of a right circular cylinder. Furthermore, as itis very clear that some correction is needed, the apparatus according to the invention achieves improved results even though the correcting surface only partly corrects the bad condition whether absolute theoretical perfection. is achieved or not. Therefore I should not be confined to the truth of my theories although I believe them to be true.

Referring now to Figure 2 the apparatus of the invention is shown as mounted on a feed slide I ll which, in the case of a grinding machine, may be the regulating wheel feed slide and in the case of a lapping, machine may be either the regulating wheel slide or the lapping wheel slide. By the movement of the slide I0 along ways not shown, the wheel is advanced toward and from 7 another wheel for purposes and in manners known to those skilled in the art. Since subject invention deals with truing and shaping of a wheel, the various parts of a complete machine under and beyond the slide I 9 need not be shown or described herein, V

Referring to Figure 2, mounted upon the wheel slide II is a wheel head II which hasa flat surface I2. The wheel head II is fastened to the slide IQ as by means of bolts I2a. Inside the wheel head H is a boss I3 which has a bore 35 bymeans of bolts 39.

a 4 in which is mounted a trunnion shaft I4. The trunnion shaft I4 extends through a yoke I 5 and journals the yoke for angular adjustment. To the right of the trunnion shaft I4 is a tightening bolt I6 having a screw threaded part i! which fits in a threaded bore I8 of the trunnion shaft I4. The tightening bolt has a portion of larger diameter than the bore in which is located the trunnion shaft I4 which leaves a shoulder I9 engaging washers 20 which thrust against the boss I3. The bolt l6 has a square head 2| so that it may be turnedwith a wrench and when this is done, a head 22 having a conical surface 23 is drawn against a conical seat 24 at one end of the bore in the yoke I5 through which the trunnion shaft I4 passes, and thereby the trunhim is tightened. Accurate centering is obtained by provision of the conical surface 23 and the conical seat 24.

Referring now to Figures 1 and2 tightening bolts 25 extend through elongated arcuate slots 26 in an arcuate flange 27 which extends upwardly from the wheel head II. These'bolts 25 extend into screw threaded holes provided in the yoke I5. The yoke I5 has a fiat surface 30 which is against the fiat surface [2 of the head II. By loosening the bolts ,25 and possibly also the bolt I6 slightly, the yoke I5'is free to be adjusted angularly on the trunnion shaft I4 to an amount allowed by'the length of the slots 26 which may be up to ten, degrees either way or sometimes more. This adjustment may be made with a lead hammer, and a scale and a lubber line, not shown, .are provided, one on the wheel head I I and the other on theyoke I5 so that the adjustment may be accurately made. After the adjustment to the desired skew angle h'as been made, the bolt I6 and the bolts 25 are tightened and this locks theyoke I5 to the wheel head II.

The yoke I5 has yoke arms which extend to the left of the base 36 of the yoke. Bearings for a wheel spindle 3! are formed half in the undersides of the-arms 35 and half in bearing blocks 36 which are removably bolted tothe arms A wheel is the wheel which is to be shaped or trued in accordance with this invention. This wheel 40 may be a feed wheel otherwise termed a regulating wheel or a control wheel, and it may additionally have the function of alapping wheel or a grinding Wheel. It may be made of various materials which can be cut or formed by a truing tool such as a diamond, but in a typical case and preferably it is an abrasive wheel madeof abrasive grain such as silicon carbide or fused alumina, bonded with a suitable bond'such'as vitrified bond, phenolic resin, rubber, shellac, etc'l Preferably for such a wheel fine grit abrasive 'is used bonded with rubber or synthetic rubber or phenolic resin. This wheel 40 is mounted in any usual manner upon the wheel spindle 31, being desirably provided with bushing plates 4| and nuts 42 which also act as spacers. v

The wheelspindle 3'! may be'driven in any usualor desired manner, Preferably some kind of speed changing mechanism is provided in order that the wheel may be driven at various regulating speeds and also at high speeds for truing. Such driving and speed changing mechanism may be mounted upon the wheel slide Ill but is not shown herein. The power may be belts to a pulley 45 interfering with tne'arive;

Extending between the yoke arms 35 at the up per, outer corners thereof is a bridge portion 46 which may be cast integral with the remainder of the yoke i5. Formed both in the base portion 36 and the bridge portion 46 of the yoke I are ways 41. These ways are curved and form part of a circle. Their surfaces are portions of the inside of a cone. Complementary and therefore exterior conical surfaces -48 (see Figure l) are formed on the underside of a large table 49 which has a long slot 59 of substantially parallelepipedal shape which is located in a mid position of the table 29, which is likewise for the most part a rectangular parallelepiped. However, the

upper portion of table 49 has dove. tail ways 5! fitting which are dove tails 52 on the underside of a slide 53. The slide 53 has a threaded bore 5d extending through it on one side, the axis of the bore being parallel to the ways 51. A screw shaft 55 extends through the'threaded bore '54 and is journalled in a boss 56 extending upwardly from the table 49. Collars 57 and 58 hold the screw shaft 55 from axial movement. A hand wheel Ed fastened to the screw shaft 55 is used to rotate it manually and when this is done the slide 53 will be moved slowly along the ways 5|. The path of movement of the slide 53 may, however, be altered with respect to the axis of the Wheel 4E by adjusting the table 59 on the circular ways 41. In this manner the skew angle of the truing device is established. A scale and a lubber line, not shown, are preferably provided, one on the table 49 and the other on some part of the yoke i5 adjacent to the table in order that the exact amount of skew may be known. A bolt 62 extending into the underside of the table 49 and through a slot 64 in the bridge portion 45 may be used to hold the skew angle after the table 49 is set. In order that the slide 53 shall move along the table ii-3 in a perfectly straight line without deviation, there is provided between the dove tail 5! and the adjacent dove tail 52 a gib 55 and a couple of adjustment screws 66 extending part way into the gib.

In the center of the slide 53 is an upstanding cylindrical boss Hi. In this boss and extending through the slide 53 is a bore 1! the axis of which is perpendicular to the plane of the ways 51 and generally perpendicular to the axis of the spindle 3?. In this bore H is a shaft 12 the major portion of which closely fits the bore 1|. However a lower portion E3 of the shaft 12 is shown of reduced diameter which is a mere matter of clearance and dimensions and in this respect many changes might be made. The lower end of the reduced portion 73 of the shaft '12 is split in a manner not shown herein since it is well known in the art and is illustrated in Figure 9 of Patent No. 1,871,504 'to Einstein and Nenninger. In the manner shown in that patent the shaft l2 adjustably holds a slide 80 provided with a scale Bi and secured to the slide 80 is a diamond nib 82 in which is set a diamond 83 with a sharp polyhedral angle. When the zero mark of the scale 8! is opposite some fixed point of the shaft 12, for example, the left hand side of the reduced portion 13, the apex of the diamond 83 is right on the axis of the shaft 12. This is the proper setting for truing when the axis of the Work piece intersects a line extending from the exact central oint of one wheel to the exact central point of the other wheel. When the work piece is above or below this position, the slide 88 is adjusted in a manner known to those skilled in the art. Briefly the amount of offset of the diamond 83 equals the distance of the center of the work above or below the line referred to. The basic reason is that if the work is above or below the line the wheel 40, if at a skew angle, must be bigger at one end than at the other. When the adjustment has been made the split parts of the shaft 72' are clamped together by a bolt 84 to hold the slide firmly. To prevent the shaft 32 from turning there is provided a spline 8b therein in which fits a key 81 which also extends into a key seat in the boss 10.

Referring to Figure 1 as well as Figure 2 a holding member 90 has a split bore 91 fitting the shaft 12. Arms 92 extend on either side of the split and a bolt 93 passes through them. A nut 54 on the bolt 93 may be tightened thus to draw the arms 92 together and clamp the member 99 securelyto the shaft 12 in a desired position of adjustment. The member 90 has a screw threaded bore 95 parallel to the split bore 9|. In this screw threaded bore 96 is a screw shaft 91 the lower end of which has a follower point 98. The hub 99 of a hand wheel lilfl is driven onto a tapered portion ll)! of the shaft 91 and may be further secured thereto by means of a key I02 fitting in a key way E03 of the shaft 97 and also in a key seat in the hub 99. It will be clear that when the hand wheel l!!!) is turned the member 90 will be raised or lowered relative to the shaft 91. This action raises or lowers the diamond 83. The follower point 98 is exactly on the axis of the shaft 91. To look the shaft 9'! to the member 90 I provide a knurled nut I04 on the shaft 91.

The follower point 98 rests on the curved surface H0 of a long bar III which has an integral shaft H2 extending at right angles to the long bar I from its mid position. A conical seat i 13 is provided where the long bar I I I and the shaft H2 merge and rests against a conical seat H4 in the upper part of a bore H5 provided in a boss H8 which is formed as an extension of the table 49. The axis of the bore H5 is at all times parallel to the axis of the shaft 12. The long bar IH may be adjusted to any angular position and when so adjusted may be clamped in this position by means of a screw bolt i ll extending into a threaded bore i id in the shaft H2 there being a thrust washer I it between the head of the bolt H1 and the underside of the boss H6. As in the case of other adjustments scale marks and a lubber line (not shown) are provided, one on the upper surface of the boss HE and the other on the long bar HI. The'surfa-ce H0 is the surface hereinbefore referred to which may be part of a hyperbolic cylinder or may be a segment of a right circular cylinder.

Although there may be other ways, one method of making a surface which is part of a hyperbolic cylinder is known to me. Take a good surface grinder provided with a magnetic chuck and provide it with a fine grit grinding wheel. Provide a slide mechanism consisting of a base with a slide way, a slide in the slide way and secure a nib with a truing diamond to the slide. The base should be made of iron. Set the wheel spindle straight i. e. perpendicular to the motion of the slide of the surface grinder and horizontal. Place the base ofthe slide mechanism on the magnetic chuck so that the diamond will move at a slight skew angle to the wheel spindle of the surface grinder. An angle of about five degrees will give good results. Provide a hand screw feed mechanism for the slide of the slide mechanism. Now set the main slide of thesurface grinder so that the diamond will move through the vertical center line of the wheel. Then lower the wheel and true it with the diamond. Then set the long bar HI in a fixture on the magnetic chuck so that the long dimension of the long bar III is parallel to the ways of the surface grinder and so that th center of the long bar ii! is right under the central point of the grinding wheel. Now grind using traverse and downfeed but no cross feed. After the surface H has been ground the, grinding lines may be removed by careful application of fine grit abrasive paper or cloth.

The axis of the Wheel 40 is set to the desired. skew angle by adjusting the yoke H; as described. Let us suppose that this is five degrees. Then the table 49 is setto a skew angle of five degrees. If Figure 2 is a view from the front of the machine the skew of the yoke idwill be set to raise the front end of the wheel to. This will cause the work piece to feed through the grinding throat from front to back of machine as is of course desired. But except for the subsequent setting of the slide 89 (which can be set either way) it does not matter in which direction you skew the table 49 so long as the amount is the same as the skew of the yoke l5. Now the slide 80 is set for work piece above or below the center line, the work piece usually being above. Which way to set the slide 8%] depends on the other settings and is well known to those skilled in the art so no detailed rule will be given. Now the long bar H] is skewed by an amount depending upon the size of the work piece, increasing for increasing sizes of work piece. A table of skew angles for the bar ll with coordinates of skew angles of the yoke i5 and of work piece sizes will be provided. This table can be derived by mathematics.

- The above settings having been made and the wheel c6 set in rotation at a high rate of speed, the hand wheel 69 is turn d to bring the diamond 83 over one edge of the wheel 46. It is assumed that the diamond t3 was not Q low enough to make contact. Now the knurled nut lfifl-isbacked off'and the hand wheel IE8 is turned until slight contact is made between the diamond Stand the wheel to. From the construction described it will be seen that turning of the hand wheel loll raises and lowers the diamond 83. The weight of the apparatus will hold r the diamond down to some extent, but a spring I extending from the bolt 93 to an eye bolt I2! in the slide 53 may be provided to assure firm contact between therdiamond 83 and the wheel 46. superfluous since the manner of using the ap paratus will now be clear to those skilled in the art. The knurled nut M4 is tightened between adjustments and truing should be gradually accomplished to avoid burning the diamond B3 and to achieve a true shaped surface on the wheel 46.

When the long bar HE is set at zero skew, the follower 98 travels along a line which is the generatrix of the hyperbolic cylinder when it is at the vertex of the directrix hyperbola. This is a straight line and under suchconditions'the wheel 40 will be trued exactly the same as in conventional centerless grinders and with the same results. When, however, the long bar I I l is set to any skew angle, the ioilower will trace a hyper- V" bola, the less the angle, the flatter the hyperbola. The limiting hyperbole. is the directrix hyperbola which is reached when the skew angle otthe long bar III is set at 90. Of course a skew angle of 180- is the same'as a skew angleof 0and a skew:

Further instructions about operation are at zero. Now the follower 98 should ride over the vertex generatrix when the diamond 83 digs deepest into the wheel 4i (i. e. is nearest to the axis-of the wheel All). When this condition is achieved the compensation will be symmetrical to the action, i. e. the hyperbolic compensation of this invention will be symmetrical to the hyperbolic truing of the old art.

Referring now to Figures 3 and 4, I provide a long bar H lawith a hyperbolic cylindrical sur face the same as already described. Integral with the long bar ii is is a dove tail 1 which fits in a clamping member I26, the clamping member lZfi constituting ways for the dove tail member I25 whereby it may be moved perpendicularly to the long dimension of the long bar H id. The

clamping member iZfi is an integral part of a shaft HZa just like the shaft H2 and having a conical seat H30. which rests in the conical seat lid of the boss iiii. Screws izl'are provided to clamp the dove tail 25 in the adjusted position and a fine scale and a lubber line (not shown) are provided. one on the dove tail i255 and the other on the member I25 to determine the adjustment. These may be read with a magnifying glass. The setting should be such that when the diamond 83 is nearest tothe axis of the wheel 3?, the iol- 7 lower 88 is on the vertex generatrix oi the surface 0.

To recapitulate the settings, first the yoke isskewed to the desired amount and there are tables of rate of'feed of work pieces for sizes and. R. P. M. of wheels and skew angles. Next the table lfl is set to the same skew angle. Thirdly the slide is set for work piece above or below the center line of the wheels and in a direction dependent on whether above or below and in which-direction the table til was skewed. All of this is as usual and is known'to the art.

Now the angular skew of the long bar iii or H la is set according to table in which the diameter of the work piece is one entry and the skew of the table 55 is another Now another table is provided for the ad ustment oi the dove to the right.

tail in the clamping member E25 in which the position of the siide to by the scale 8! is one entry and the skew angle of long bar Mia is the other entry. This table can be made from mathematics and is based upon the particular hyperbola of the directrix of the surface lit.

There is one remaining point. If the settings which areold in the art were made so that the far end of the wheel 37 will be larger than the near end to correspond with Work piece above the center lineyand the skew 0f the long bar' i I la is clockwise in plan View, the dove tail I25 is moved Forextreme settings of the slide 86 the follower 98'may be always to one side of 1 the vertex generatrix.

It will thus be seen that there has been provided by this invention an apparatus in which the'various objects hereinabove set forth together with manythoroughly practical advantages are might be made in the embodiment above set forth,

it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a truing apparatus having a spindle for the wheel to be trued, a truing diamond, means including a slideway and a slide thereon for moving said diamond rectilinearly, angularly adjustable skew means whereby the slide will move the diamond parallel to the axis of the spindle or at a skew angle thereto, a mounting for the diamond in the slide whereby the diamond can move towards or away from the spindle as the slide moves, and afollower having a point, the combination with said truing apparatus of a template member for said follower having a surface generated from a straight line moving along a curve as directrix, one of the last two parts being connected to the mounting for the diamond and the other stationary with respect to the slideway but adjustable angularly relative thereto, whereby the diamond moves and out as the follower follows the surface to correct the truing.

2. In a truing apparatus having a spindle for a wheel to be trued, a siideway, skew means to adjust the slideway angularly relative to the axis of the spindle, a slide on the slicleway, and a truing member mounted on the slide and having a truing point, the member being mounted for movement of the truing point towards and away from the axis of the spindle, the combination with said truing apparatus of means for giving the point a slight movement in the direction towards and away from the said axis as the slide moves, said last named means comprising a pointed member and a curved surface, one connected to the truing member and the other to the slideway, the surface being angularly adjustable and being a hyperbolic cylinder.

3. In a truing apparatus having a spindle for a wheel to be trued, a truing tool, means to move the truing tool at a skew angle to the spindle, and a mounting for the truing tool permitting it to move towards and from the spindle as it is moved at the skew angle, the combination with said truing apparatus of means including a follower and a surface to cause said truing tool to move towards and from the spindle as it is moved, said surface being a hyperbolic cylinder so that the truing tool moves in a hyperbolic path.

4. In apparatus as claimed in claim 3, the combination with the parts and features therein specified, of an adjustment whereby any one of an infinite number of hyperbolic paths may be selected.

5. In a truing apparatus having a spindle for the wheel to be trued, a truing tool, means for moving the truing tool in a path which makes a skew angle to the axis of the spindle, and a mounting permitting movement or" the truing tool transverse to said path so that the tool may approach and recede from said axis, the combination with said truing apparatus of means for moving said truing tool transversely as it moves in said skew path comprising a part having a follower point, a part having a surface generated by moving a straight line along a curve as directrix, one of said parts being connected to said tool and the other being stationary with respect to said tool as it moves, and means for angularly adjusting said surface with respect to said path.

6. In a truing apparatus having a spindle for the wheel to be trued, a truing tool, means for moving the truing tool in a path which makes a skew angle to the axis of the spindle, and a mounting permitting movement of the truing tool transverse to said path so that the tool may approach and recede from said axis, the combination with said apparatus of means for moving said truing tool transversely as it moves in said skew path comprising a part having a follower point, a part having a surface generated by moving a straight line along a curve as directrix, one of said parts being connected to said tool and the other being stationary with respect to said tool as it moves, means for angularly adjusting said surface with respect to said part, and a transverse adjustment for one part with respect to the other part to select different paths on the surface for said follower point.

GEORGE CROMPTON, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,750,175 Holmes Mar. 11, 1930 1,772,544 Heim Aug. 12, 1930 1,825,753 Nenninger Oct. 6, 1931 1,871,504 Einstein et a1 Aug. 16, 1932 1,940,214 Holmes Dec. 19, 1933 

